Objective To study the fracture failure reasons of fastening bolt present in a military used wind driven generator. Methods The facture failure reasons of fastening bolt on a military used wind driven generator were analyzed by taking advan-tage of chemical composition analysis, mechanics property analysis, fracture scanning analysis as well as microstructure anal-ysis and testing.Results The original folded defects at the bottom of fracture bolt thread provided a beneficial condition for the fatigue crack. Meanwhile, there were some abnormalities concerning assembly among the bolt head, fastening washer and flange plate. Hence the contacting area got higher centralized stress under the effect of the external force, making for generation and further expansion of fatigue facture.Conclusion Sstrict quality control of incoming bolts, regular check of bolt in service condition, and timely replacement of bolt with potential safety hazards contribute to preventing the fastening bolt from fracture failure again.%目的：研究风力发电机紧固螺栓断裂失效原因。方法通过化学成分分析、力学性能分析、断口扫描分析、显微组织分析测试手段，对风力发电机紧固螺栓失效原因进行分析。结果断裂螺栓螺纹根部表面存在原始折叠缺陷，为疲劳裂纹的萌生提供了有利条件；同时，螺栓头部、紧固垫圈及法兰盘之间存在装配异常情况，外力作用下接触位置应力集中较大，有利于疲劳裂纹的萌生及进一步扩展。结论通过严格控制入厂螺栓质量，同时定期检查在服役螺栓的使用状态，及时更换存在安全隐患的螺栓，有效杜绝了紧固螺栓断裂失效情况再次发生。
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